The case appears to be based on the statements of one Amazon salesperson, who may well have been out of line when he spoke. Without more, it is hard to judge the strength of plaintiff's position, but if that's all there is to it, I think the case is weak.

I think you are misreading the filing. The named individual in the filing is simply the person who wrote to this particular publisher. The point of the class action is that they claim that Amazon has communicated with other POD publishers in the same terms. Such a move has been widely reported and commented upon, so the case is unlikely to rely on the actions of one rogue salesperson.